The invention relates to an eyeglass lens, in particular one having a cross-section perpendicular to the optical axis that corresponds to an eyeglass lens opening in a selected eyeglass frame or, in the case of rimless or partially framed eyeglasses, to a selected shape, and having at least one structural element applied to the eyeglass lens, preferably on outer and/or front or rear face. The invention relates to a method of making such an eyeglass lens.
Such a structural element can, for example, connect the eyeglass lens and the eyeglass frame according to the known prior art.
Moreover, at least in the case of eyeglasses that are customized for the eyeglass wearer by an optician, the eyeglass lens is centered with respect to the optical axis of the eyeglass wearer's eye by such a structural element and the positioning thereof at/on the eyeglass lens. At least in such a case a structural element also has the function of a centering structural element.
The structural element can be constructed so that it engages in a faceted groove of an eyeglass frame and/or receives the filament of a Nylor frame or produces a clippable connection to the frame.
U.S. Pat. No. 4,921,341 describes an eyeglass lens with a deformable profiled ring glued onto the edge or with an inner undercut that engages in a circumferential groove in the edge of the eyeglass lens.
A method and a device for application of a profiled strip to the contour-machined edge of a rotating eyeglass lens is described in DE 39 08 095 [U.S. Pat. No. 5,007,977]. In this case the profiled strip is laid around the entire circumference of the eyeglass lens, following the three-dimensional curve of the lens edge. For this purpose the profiled start of a continuous strip is joined to the lens edge, a transverse perforation is made in the strip at a distance from the start of the profiled strip that corresponds to the circumference of the lens, the lens is rotated and the profiled strip section is stopped downstream of the perforation in the direction of movement of the profiled strip so that the perforation point severs, after which the new leading end of the strip formed thereby for the next lens that is not yet connected to the lens edge of the first eyeglass lens is pressed against the edge of the next eyeglass lens and connected thereto. In this case the profiled strip is glued on, welded on or lasered on.
In patent document DE 100 50 007 a method is described for positioning a profiled strip on the edge of an eyeglass lens that fixes the position of the profiled strip under CNC control according to a predetermined contour. The fastening on the eyeglass lens takes place then by activation or curing of a glue between the profiled ring and the eyeglass lens.
The methods described in these publications are based on the fundamental idea that the facets hitherto ground out of the basic lens material on eyeglass lens grinding machines can be replaced by a circumferential profiled strand or a profiled strip.
Although in CNC-controlled eyeglass lens edge-grinding machines it is possible for the facet contour of a facet to be ground conform to the contour of the faceted groove of a selected eyeglass frame, the eyeglass lens with the ground facets is completely inelastic, so that stresses from the eyeglass frame are transmitted to the eyeglass lenses during installation.
Due to temperature changes stresses can also be produced that in particular plastic lenses are sensitive to and that tend to cause cracks. An applied profiled strand could consist of an elastic material and thus enable a substantially better adaptation to the frame shape.
Furthermore, the manufacturing process would be substantially simplified and would allow the use of alternative manufacturing processes, such as for example laser cutting, since a two-dimensional manufacturing process is sufficient in order to produce an edge shape that is flat or only slightly curved in the direction of the optical axis.
Furthermore, the grinding of a facet represents an additional operation that in particular considerably prolongs the automated edge machining because of the necessary precision.
The methods and concepts shown in the cited publications have not been successful hitherto on the market, in spite of the advantages by comparison with the prior art. This is cause inter alia by the following points:                The handling of separate profiled strips and bonding adhesives is difficult in practice and significantly increases the complexity of the machines.        The shape of the glued or extruded profiled strands cannot be easily adapted to different geometries of the frame groove.        Eyeglass lenses can have very thin edge regions locally, the application of a profiled strand in these regions is difficult, and projection of the profiled section over the edge of the eyeglass lens is not accepted.        The long-term durability and load-bearing capacity of compositions with contact adhesives, such as used in profiled strips, is critical taking into account the environmental influences (sunlight, sweat).        